Pivoted snap switch having manual actuating lever



1954 K. BlLLE-KNUDSEN 3,

PIVOTED SNAP SWITCH HAVING MANUAL ACTUATING LEVER Filed May 11, 1961 United States Patent 3,117,198 PHVOTED SNAP S'Wl'ltlll HAVING MANUAL ACTUATENG LEVER Klaus Billie-Knudsen, Sonderborg, Denmark, assignor to Dantoss ved ing. M. tllansen, Nordborg, Denmark, a company of Denmark Fiied May 11, 1961, Ser. No. 129,1ti2

Claims priority, application Denmark May 11, 1960 5 Claims. ((11. 20tl67) The present invention concerns a switching system with tilt mechanism and adjustable contact separation of the type employing a sprung tilt arm which, for the purpose of actuating a biased contact spring, is so connected through a tension spring to a pivoted operating arm, that an external force applied to the operating arm is transmitted to the tilt arm.

The aim of this invention is to design a switching system with one adjustable contact separation in an operating position, and a much greater separation in a manually disengaged position. A switching system of this type is primarily intended for use with thermostats, pressostats and similar instruments. In the thermostat of an evaporator, very little contact separation, e.g. a few tenths of a millimeter, is desired in the operating position, Whereas in the disengaged position a much greater contact separation, for example 3 millimeters or more, is required. Through the present invention a design has been provided which renders it possible by differential adjustment to alter the contact separation in the operating position and to retain the wide contact separation in the manually disengaged position. The switching system according to the invention is of the type which is open in the absence of an external force, and is characterized by an adjustable stop, which is so connected to the operating arm, that during transfer of the latter from a disengaged position with wide contact separation to an operating position with narrow contact separation, the stop will actuate the tilt arm to snap through its dead center position, and in the operating position of the operating arm will form an adjustable stop for the tilt arm when the contact breaks.

One embodiment of the switching system according to the invention is characterized by the fact that the adjustable stop is in the form of an adjustable screw situated on the operating arm nearer the rotating center of the arm than the point to which external force is applied. A switching system like this is comparatively simple and robust, and the external force to be applied to the operating arm can be comparatively small, because the arm functions as a lever.

Another embodiment of the switching system according to the invention is characterized by the fact that the stop is formed by that end of a two-armed lever, the fulcrum of which is supported by the arm transferring the force, which is nearer the pivot of the arm that the point to which the external force is applied.

The other end of said two-armed lever will bear against an adjustable stop which is screwed into a stationary part of the system. This arrangement renders the leverage higher, and consequently, a smaller force is required for engagement, and a wide contact separation in response to a slight movement of the operating arm is also achieved. Another advantage offered by this embodiment is the position of the adjusting screw in the switch housin which greatly facilitates adjustment.

According to the invention it is appropriate that the contact spring biased towards the fixed contact be provided with a U-shaped bent portion at its free end, in which bent portion the tilt arm can move. Hereby a high speed of transfer between engagement and disengagement of the movable contact member of the system lt atented Jan. 7, 1954 is achieved, and according to the invention, contact bounce can be considerably reduced since, that the tilt arm is fitted with a stop which is so placed, that in the closed position of the system the stop will bear against the contact spring immediately at that side of the movable contact which is nearest the fixing point of the contact spring.

In the following the invention will be explained in detail with reference to the drawing, Where:

FIGURES 1 and 2 show a first embodiment of a contact system according to the invention in disengaged and operating position, respectively, the contact being engaged in the latter position; and

FIGURES 3 to 5 show a second embodiment of the switching system according to the invention in disengaged position and operating position with the contact open and closed, respectively.

An operating arm or main lever 1, which serves for the transfer of an external force to the switching system, is pivotally mounted at a fixed point 2. The arm is in the shape of an inverted U, one leg being extended farther downwards than the other end and being supported by its pivoted end at the point 2. A tension spring 3 connects the free end of the operating arm 1 to a point 5 on a tilt arm or lever 6, which is supported in a fixed knife-edge bearing 7. The tilt arm 6 will actuate a contact elastic or spring lever 8 in the form of a leaf spring. The spring 3 biases the lever 6 to a rest position and applies a rotational force to the lever 1 in a counterclockwise direction holding the free end of the lever 1 from rotating clock wise. The free end of the contact spring carries the movable contact 9 of the system, and the other end of the contact spring is secured at the point 10 with a bias towards the fixed contact 11 of the system, thus oflering suflicient contact pressure until the contact is snapped off. The low position of the pivot 2 of the operating arm 1 in relation to the fixing point of the spring 3 will cause the operating arm to assume the disengaged position when not influenced by an external force.

The underside of the tilt arm 6 is fitted with a stop 12, which reduces contact bounce, if any, because the stop bears against a point immediately at that side of the contact which faces the fixing point Jill, thus forming here a node for any oscillation of the contact spring 8.

FIGURES 1 and 2 show a simple switching system according to the invention where an adjusting screw 12 in the operating arm 1 forms an adjustable stop through which the contact separation in the operating position can be adjusted. When the system is being engaged into the operating position the operating arm is influenced by an external or counter rotational force P, and acts through the adjusting screw 12 as a lever upon the tilt arm 6, thus reducing the force P required for engagement. When in the operating position, FIG. 2, a force p from an evaporator thermostat, for example, is applied to the operating arm. Suppose the pressure p is reduced, the tension spring 3 will pull the arm ll upwards until the points 4, 5 and 7 are on a line, whereupon the tilt arm at a continued slight movement of the arm 1 snaps upwards, hitting a U-shaped bent portion 1-3 at the free end of the contact spring 8 and thus separating the contacts 9 and 11. Since the contact spring 8 is biased towards the fixed contact 11 the contact pressure is maintained until the tilt arm 6 at high speed hits the lost motion connection means comprising U-shaped end 13 of the spring 8. The transfer continues until the tilt arm 6 bears against the adjustable stop, in this cause adjusting screw 12'. Suppose the pressure p increases again, the arm 1 moves downwards at the same time as the adjusting screw 12' moves downwards until the three points 4, 5 and 7 are on a line again. Now, a slight increase in pressure will cause the tilt arm 6 to snap over, thus causing the contact spring 8 to continue its downward transfer at a 3 higher speed until the stop i2 on the tilt arm 6 hits the spring 8.

The switching system shown in FIGURES 3 to 5 operates in the same way, but diiiers from the other system in that the arm 1 is provided with a bearing 14 which supports a two-armed lever carrying a stop 16 at one end, which stop during transfer from the disengaged position to the operating position actuates the tilt arm 6. At the opposite end the two-armed lever will bear against an adjusting screw 17 which is statically mounted on the switch housing, and therefore easy to adjust. In the same way as described above, the stop '16 will exert a pressure on the upper side of the tilt arm 6 until the arm has passed through the dead center position, when the system is switched into the operating position by applying manually a force P to the arm 1, FIG. 3. When an external force P is applied to the arm 1 in the operating position the movable contact will snap upwards r downwards at varying pressure between the positions shown in Fl URES 4 and 5. It will be seen that employment of the two-armed lever 15 in this design brings about a higher leverage than is the case in the design shown in FIG- URES 1 and 2, thus requiring a lesser force P for control of the switch.

Further, a wider contact separation is achieved through less movement of the power transferring arm 1. if the pressure 2 increases when the tilt arm is in the position shown in FIG. 4, the arm 1 moves downwards, but at the same time the two-armed lever 15 pivots in the bearing 14, causing the tilt arm 6 to be depressed faster than was the case previously, and when the three points 4-, 5 and 7 are on a line, the tilt arm snaps over in the position shown in FIG. 5. When the pressure p is relieved again, the tilt arm 6 snaps upwards carrying the contact spring 8 with it, until it hits the stop 16, which is prevented from moving any farther, because the lever arm bears against the adjusting screw 17.

The efiect described above may also be achieved by letting the said levers actuate the contact spring directly.

What I claim and desire to secure by Letters Patent is:

1. In a snap switch in combination, a stationary contact, an elastic lever having one end pivoted and another end free biased in a direction toward said fixed contact, a contact on said elastic lever disposed for engaging said fixed contact when said spring lever is free to move in a direction toward said stationary contact a distance suiiicient for closing said contacts at a contact-closing position of said elastic lever, means for controllably operating said elastic lever to said contact-closing position and to a position for maintaining said contacts in a separated and electrically open position comprising, a main lever having one end pivotally secured and another end free, said pivotally secured end of the main lever being disposed vertically and horizontally closer to said fixed contact than said free end of said main lever, said elastic lever extending in a plane parallel to the main lever, a contactactuating third lever having one end pivoted at a stationary point and an opposite free end, means elastically applying a force on said third lever toward said stationary point and rotationally and toward a rest position of said third lever and cooperating therewith for urging pivotally rotationally said free end of said main lever a limited extent in a direction toward the free end of said third lever, said elastic means being connected to said main lever at a fixed point thereon movable in conjunction with said main lever and to a fixed point on said third lever movable in conjunction with said third lever, said stationary point at which said third lever is pivoted being disposed in a position intermediate said movable points on said third and main levers, lost-motion connection means releasably connecting the free ends of said elastic lever and said third lever and having means effective to allow said third lever to hold said free end of said elastic lever apart from said stationary contact spacing said contacts when said third lever is in said rest position and said main lever is free to be rotationally urged cooperatively by said third lever and said elastic means in the absence of a counter rotational force and effective to allow free movement of said elastic lever to said contact-closing position when said counter rotational force is applied, said fixed points on said lain and third levers and said stationary point on which said third lever is pivoted being disposed to lie in operation on a common center-line plane and to jointly be disposed in said plane during operational actuation of said switch so that upon application of a counter rotational force rotating said main lever in a direction opposite to which said elastic means urges said main lever said elastic means snaps said third lever to a position opposite to said center-line plane from said rest position to cause said connection means to release said elastic lever for engaging said contacts and upon cessation of said counter rotational force said elastic means biases the main lever to said rotated position and snaps the third lever to said rest position and said third lever causes said connection means to connect the third lever and elastic lever to snap apart said contacts, and adjustable stop means mounted on said main lever to determine the rest position of said third lever and for controlling the distance said contacts are spaced apart when said third lever is in said rest position and the distance said third lever free end is from said center-line plane and thus to variably control the value of the counter rotational force necessary to close said switch and maintain it closed.

2. In a snap switch in combination, a stationary cona contact on said elastic lever disposed for engaging said.

fixed contact when said spring lever is free to move in a direction toward said stationary contact a distance suiticient for closing said contacts at a contact-closing position of said elastic lever, means for controllably operating said elastic lever to said contact-closing position and to a position for maintaining said contacts in a separated and electrically open position comprising, a main lever having one end pivotally secured and another end free, said pivotally secured end of the main lever being disposed vertically and horizontally closer to said fixed contact than said free end of said main lever, said elastic lever extending in a plane parallel to the main lever, a contact-actuating third lever having one end pivoted at a stationary point and an opposite free end, means elastically applying a force on said third lever toward said stationary point and rotationally and toward a rest position of said third lever and cooperating therewith for urging pivotally rotationally said free end of said main lever a limited extent in adirection toward the free end of said third lever, said elastic means being connected to said main lever at a fixed point thereon movable in conjunction with said main lever and to a fixed point on said third lever movable in conjunction with said third lever, said stationary point at which said third lever is pivoted being disposed in a position intermediate said movable points on said third and main levers, lost-motion connection means releasably connecting the free ends of said elastic lever and said third lever and having means effective to allow said third lever to hold said free end of said elastic lever apart from said stationary contact spacing said contacts when said third lever is in said rest position and said main lever is free to be rotationally urged cooperatively by said third lever and said elastic means in the absence of a counter rotational force and effective to allow free movement of said elastic lever to said contact-closing position when said counter rotational force is applied, said fixed points on said main and third levers and said stationary point on which said third lever is pivoted being disposed to lie in operation on a common center-line plane and to jointly be disposed in said plane during operational actuation of said switch so that upon application of a counter rotational force rotating said main lever in a direction opposite to which said elastic means urges said main lever said elastic means snaps said third lever to a position opposite to said centerline plane from said rest position to cause said connection means to release said elastic lever for engaging said contacts and upon cessation of said counter rotational force said elastic means biases the main lever to said rotated position and snaps the third lever to said rest position and said third lever causes said connection means to connect the third lever and elastic lever to snap apart said contacts, adjustable stop means mounted on said main lever to determine the rest position of said third lever and for controlling the distance said contacts are spaced apart when said third lever is in said rest position and the distance said third lever free end is from said center-line plane and thus to variably control the value of the counter rotational force necessary to close said switch and maintain it closed, and said main lever having a surface for applying said counter rotational force.

3. In a snap switch in combination, a stationary contact, an elastic lever having one end pivoted and another end free biased in a direction toward said fixed contact, a contact on said elastic lever disposed for engaging said fixed contact when said spring lever is free to move in a direction toward said stationary contact a distance sufficient for closing said contacts at a contact-closing position of said elastic lever, means for controllably operating said elastic lever to said contact-closing position and to a position for maintaining said contacts in a separated and electrically open position comprising, a main lever having one end pivotally secured and another end free, said pivotally secured end of the main lever being disposed vertically and horizontally closer to said fixed contact than said free end of said main lever, said elastic lever extending in a plane parallel to the main lever, a contact-actuating third lever having one end pivoted at a stationary point and an opposite free end, means elastically applying a force on said third lever toward said stationary point and rotationally toward a rest position of said third lever and cooperating therewith for urging pivotally, rotationally said free end of said main lever a limited extent in a direction toward the free .end of said third lever, said elastic means being connected to said main lever at a fixed point thereon movable in conjunction with said main lever and to a fixed point on said third lever movable in conjunction with said third lever, said stationary point at which said third lever is pivoted being disposed in a position intermediate said movable points on said third and main levers, lost-motion connection means releasably connecting the free ends of said elastic lever and said third lever and having means effective to allow said third lever to hold said free end of said elastic lever apart from said stationary contact spacing said contacts when said third lever is in said rest position and said main lever is free to be rotationally urged cooperatively by said third lever and said elastic means in the absence of a counter rotational force and effective to allow free movement of said elastic lever to said contact-closing position when said counter rotational force is applied, said fixed points on said main and third levers and said stationary point on which said third levers is pivoted being disposed to lie in operation on a common center-line plane and to jointly be disposed in said plane during operational actuation of said switch so that upon application of a counter rotational force rotating said main lever in a direction opposite to which said elastic means urges said main lever said elastic means snaps said third lever to a position opposite to said center-line plane from said rest position to cause said connection means to release said elastic lever for engaging said contacts and upon cessation of said counter rotational force said elastic means biases the main lever to said rotated position and snaps the third lever to said rest position and said third lever causes said connection means to connect the third lever and elastic lever to snap apart said contacts, and adjustable stop means mounted on said main lever to determine the rest position of said third lever and for controlling the distance said contacts are spaced apart when said third lever is in said rest position and the distance said third lever free end is from said centerline plane and thus to variably control the value of the counter rotational force necessary to close said switch and maintain it closed, and said main lever having a surface for applying said counter rotational force in a plane between the free end of said main lever and said stationary pivot joint of said third lever.

4. In a snap switch in combination, a stationary contact, an elastic lever having one end pivoted and another end free biased in a direction toward said fixed contact, a contact on said elastic lever disposed for engaging said fixed contact when said spring lever is free to move in a direction toward said stationary contact a distance sufficient for closing said contacts at a contact-closing position of said elastic lever, means for controllably operating said elastic lever to said contact-closing position and to a position for maintaining said contacts in a separated and electrically open position comprising, a main tlever having one end pivotally secured and another end free, said pivotally secured end of the main lever being disposed vertically and horizontally closer to said fixed contact than said free end of said main lever, said elastic lever extending in a plane parallel to the main lever, a contact-actuating third lever having one end pivoted at a stationary point and an opposite free end, means elastically applying a force on said third lever toward said stationary point and rotationally toward a rest position of said third lever and cooperating therewith for urging pivotally, rotationally said free end of said main lever a limited extent in a direction toward the free end of said third lever, said elastic means being connected to said main lever at a fixed point thereon movable in conjunction with said main lever and to a fixed point on said third lever movable in conjunction with said third lever, said stationary point at which said third lever is pivoted being disposed in a position intermediate said movable points on said third and main levers, lost-motion connection means releasably connecting the free ends of said elastic lever and said third lever and having means elfective to allow said third lever to hold said free end of said elastic lever apart said stationary contact spacing said contacts when said third lever is in said rest position and said main lever is free to be rotationally urged cooperatively by said third lever and said elastic means in the absence of a counter rotational force and elfective to allow free movement of said elastic lever to said contact-closing position when said counter rotational force is applied, said fixed points on said main and third levers and said stationary point on which said third lever is pivoted being disposed to lie in operation on a common center-line plane and to jointly be disposed in said plane during operational actuation of said switch so that upon application of a counter rotational force rotating said main lever in a direction opposite to which said elastic means urges said main lever said elastic means snaps said third lever to a position opposite to said center-line plane from said rest position to cause said connection means to release said elastic lever for engaging said contacts and upon cessation of said counter rotational force said elastic means biases the main lever to said rotated position and snaps the third lever to said rest position and said third lever causes said connection means to connect the third lever and elastic lever to snap apart said contacts, and adjustable stop means comprising a threaded screw mounted on said main lever and engaging said third lever to determine the rest position of said third lever and for controlling the distance said contacts are spaced apart when said third lever is in said rest position and the distance said third lever free end is from said centerline plane and thus to variably control the value of the counter rotational force necessary to close said switch and maintain it closed, and said main lever having a surface for applying said counter rotational force.

5. In a snap switch in combination, a stationary contact, an elastic lever having one end pivoted and another end free biased in a direction toward said fixed contact, a contact on said elastic lever disposed for engaging said fixed contact when said spring lever is free to move in a direction toward said stationary contact a distance sufficient for closing said contacts at a contact-closing position of said elastic lever, means for controllably operating said elastic lever to said contact-closing position and to a position for maintaining said contacts in a separated and electrically open position comprising, a main lever having one end pivota lly secured and another end free, said pivotally secured end of the main lever being disposed vertically and horizontally closer to said fixed contact than said free end of said main lever, said elastic lever extending in a plane parallel to the main lever, a contact-actuating third lever having one end pivoted at a stationary point and an opposite free end, means elastically applying a force on said third lever toward said stationary point and rotationally toward a rest position of said third lever and cooperating therewith for urging pivotally rotationally said free end of said main lever a limited extent in a direction toward the free end of said third lever, said elastic means being connected to said main lever at a fixed point thereon movable in conjunction with said main lever and to a fixed point on said third lever movable in conjunction with said third lever, said stationary point at which said third lever is pivoted being disposed in a position intermediate said movable points on said third and main levers, connection means releasably connecting the free ends of said elastic lever and said third lever and having means effective to allow said third lever to hold said free end of said elastic lever apart from said stationary contact spacing said contacts when said third lever is in said rest position and said main lever is free to be rotationally urged cooperatively by said third lever and said elastic means in the absence of a counter rotational force and effective to allow free movement of said elastic lever to said contact-closing position when said counter rotational force is applied, said fixed points on said main and third levers and said stationary point on which said third lever is pivoted being disposed to lie in operation on a common center-line plane and to jointly be disposed in said plane during operational actuation of said switch so that upon application of a counter rotational force rotating said main lever in a direction opposite to which said elastic means urges said main lever said elastic means snaps said third llever to a position opposite to said center-line plane from said rest position to cause said connection means to release said elastic lever for engaging said contacts and upon cessation of said counter rotational force said elastic means biases the main lever to said rotated position and snaps the third lever to said rest position and said third lever causes said connection means to connect the third lever and elastic lever to snap apart said contacts, and adjustable stop means comprising a pivoted stop lever mounted on said main lever having a surface positionable to determine the rest position of said third lever and for controlling the distance said contacts are spaced apart when said third lever is in said rest position and the distance said third lever free end is from said centerline plane and thus to variably control the value of the counter rotational force necessary to close said switch and maintain it closed, means to bias the stop lever controllably into engagement with said third lever, and said main lever having a surface for applying said counter rotational force.

References Cited in the file of this patent UNITED STATES PATENTS Turner et a1. Oct. 5, 

1. IN A SNAP SWITCH IN COMBINATION, A STATIONARY CONTACT, AN ELASTIC LEVER HAVING ONE END PIVOTED AND ANOTHER END FREE BIASED IN A DIRECTION TOWARD SAID FIXED CONTACT, A CONTACT ON SAID ELASTIC LEVER DISPOSED FOR ENGAGING SAID FIXED CONTACT WHEN SAID SPRING LEVER IS FREE TO MOVE IN A DIRECTION TOWARD SAID STATIONARY CONTACT A DISTANCE SUFFICIENT FOR CLOSING SAID CONTACTS AT A CONTACT-CLOSING POSITION OF SAID ELASTIC LEVER, MEANS FOR CONTROLLABLY OPERATING SAID ELASTIC LEVER TO SAID CONTACT-CLOSING POSITION AND TO A POSITION FOR MAINTAINING SAID CONTACTS IN A SEPARATED AND ELECTRICALLY OPEN POSITION COMPRISING, A MAIN LEVER HAVING ONE END PIVOTALLY SECURED AND ANOTHER END FREE, SAID PIVOTALLY SECURED END OF THE MAIN LEVER BEING DISPOSED VERTICALLY AND HORIZONTALLY CLOSER TO SAID FIXED CONTACT THAN SAID FREE END OF SAID MAIN LEVER, SAID ELASTIC LEVER EXTENDING IN A PLANE PARALLEL TO THE MAIN LEVER, A CONTACTACTUATING THIRD LEVER HAVING ONE END PIVOTED AT A STATIONARY POINT AND AN OPPOSITE FREE END, MEANS ELASTICALLY APPLYING A FORCE ON SAID THIRD LEVER TOWARD SAID STATIONARY POINT AND ROTATIONALLY AND TOWARD A REST POSITION OF SAID THIRD LEVER AND COOPERATING THEREWITH FOR URGING PIVOTALLY ROTATIONALLY SAID FREE END OF SAID MAIN LEVER A LIMITED EXTENT IN A DIRECTION TOWARD THE FREE END OF SAID THIRD LEVER, SAID ELASTIC MEANS BEING CONNECTED TO SAID MAIN LEVER AT A FIXED POINT THEREON MOVABLE IN CONJUNCTION WITH SAID MAIN LEVER AND TO A FIXED POINT ON SAID THIRD LEVER MOVABLE IN CONJUNCTION WITH SAID THIRD LEVER, SAID STATIONARY POINT AT WHICH SAID THIRD LEVER IS PIVOTED BEING DISPOSED IN A POSITION INTERMEDIATE SAID MOVABLE POINTS ON SAID THIRD AND MAIN LEVERS, LOST-MOTION CONNECTION MEANS RELEASABLY CONNECTING THE FREE ENDS OF SAID ELASTIC LEVER AND SAID THIRD LEVER AND HAVING MEANS EFFECTIVE TO ALLOW SAID THIRD LEVER TO HOLD SAID FREE END OF SAID ELASTIC LEVER APART FROM SAID STATIONARY CONTACT SPACING SAID CONTACTS WHEN SAID THIRD LEVER IS IN SAID REST POSITION AND SAID MAIN LEVER IS FREE TO BE ROTATIONALLY URGED COOPERATIVELY BY SAID THIRD LEVER AND SAID ELASTIC MEANS IN THE ABSENCE OF A COUNTER ROTATIONAL FORCE AND EFFECTIVE TO ALLOW FREE MOVEMENT OF SAID ELASTIC LEVER TO SAID CONTACT-CLOSING POSITION WHEN SAID COUNTER ROTATIONAL FORCE IS APPLIED, SAID FIXED POINTS ON SAID MAIN AND THIRD LEVERS AND SAID STATIONARY POINT ON WHICH SAID THIRD LEVER IS PIVOTED BEING DISPOSED TO LIE IN OPERATION ON A COMMON CENTER-LINE PLANE AND TO JOINTLY BE DISPOSED IN SAID PLANE DURING OPERATIONAL ACTUATION OF SAID SWITCH SO THAT UPON APPLICATION OF A COUNTER ROTATIONAL FORCE ROTATING SAID MAIN LEVER IN A DIRECTION OPPOSITE TO WHICH SAID ELASTIC MEANS URGES SAID MAIN LEVER SAID ELASTIC MEANS SNAPS SAID THIRD LEVER TO A POSITION OPPOSITE TO SAID CENTER-LINE PLANE FROM SAID REST POSITION TO CAUSE SAID CONNECTION MEANS TO RELEASE SAID ELASTIC LEVER FOR ENGAGING SAID CONTACTS AND UPON CESSATION OF SAID COUNTER ROTATIONAL FORCE SAID ELASTIC MEANS BIASES THE MAIN LEVER TO SAID ROTATED POSITION AND SNAPS THE THIRD LEVER TO SAID REST POSITION AND SAID THIRD LEVER CAUSES SAID CONNECTION MEANS TO CONNECT THE THIRD LEVER AND ELASTIC LEVER TO SNAP APART SAID CONTACTS, AND ADJUSTABLE STOP MEANS MOUNTED ON SAID MAIN LEVER TO DETERMINE THE REST POSITION OF SAID THIRD LEVER AND FOR CONTROLLING THE DISTANCE SAID CONTACTS ARE SPACED APART WHEN SAID THIRD LEVER IS IN SAID REST POSITION AND THE DISTANCE SAID THIRD LEVER FREE END IS FROM SAID CENTER-LINE PLANE AND THUS TO VARIABLY CONTROL THE VALUE OF THE COUNTER ROTATIONAL FORCE NECESSARY TO CLOSE SAID SWITCH AND MAINTAIN IT CLOSED. 